OK ... GJ. I worked on several projects there over the years so I know the town. Unfortunately, photography is only a hobby, so my work in GJ does not equal photo knowledge. Here's what I can recommend from the few half days I have been able to sneak away with a camera.

Colorado National Monument (already mentioned).

Grand Mesa (already mentioned).

Highway 141 (already mentioned).

Although I've never been there, Google Maps says it's about 2 1/2 hours to Dinosaur National Monument from Grand Junction - if that's something you're interested in, it could make for a day trip. Glenwood Canyon is also a day trip, about 60-90 minutes east of GJ along I-70.

Closer to town, you can go east into De Beque Canyon along the Colorado River (take I-70 east out of town and you'll wind up in the canyon in 15-20 minutes). There are both local and state parks along the river between GJ and Palisade, CO. Google James Robb Colorado River State Park and Palisade Riverbend Park. These parks allow you to photograph the river and surrounding habitat, often with the cliffs of the canyon in the background. I-70 provides the majority of access, but in areas where US 6 is a separate roadway, US 6 is better for local access. There is also a "parking area" off of eastbound I-70 (no westbound access) that follows the river in the canyon while the interstate goes through a short tunnel. The parking area provides easy access for "stop the car and step out" photography.

In town, there is the Western Colorado Botanic Gardens and Butterfly House (Struthers & S 7th Street) along the Colorado River near downtown. Take Riverside Parkway to S 7th Street and go 1 block south to Struthers and the entrance. There's also a tiny trailhead / parking lot on the west side of town that provides access to the Colorado River trail system on the north side of the river. The trailhead is just south of I-70B where 24 Road (north-south street) becomes Redlands Pkwy (east-west street). Access is a bit goofy due to some one-way roads off Redlands Parkway, but put 39.08944,-108.61173 into Google Maps or your favorite GPS/mapping app and you should be able to get there.